The present invention generally relates to radio communications systems, and more particularly, to a digital radio communications system having a data generating node and a data receiving node. The data receiving node further provides a backlink command feature that allows the data receiving node to issue commands that may be used to alter the operating characteristics of the data generating node.
Progress in affordable wet-end sensor technology may be outstripping the concomitant data-relay capability, leaving the oceanographic and surveillance communities with instrumentation that contains inexpensive sensing capability tied to cumbersome, expensive, shore-landing trunk cables. In some circumstances, a buoyed RF data relay just outside the surf zone would mitigate much of the problem by not exposing the trunk cable to breaking surf. However, such systems have relatively high power consumption requirements and low data throughput rates. Existing data links associated with ocean-deployed sensor arrays are very large and use batteries encased in a sealed container that may reside on the sea floor. Such power supplies usually have a lifetime of less than 48 hours. Another type of data link buoy developed at the U.S. Naval Research Laboratory is capable of prolonged deployments, but relies on a diesel-driven electrical generator for power. The buoy is so large and heavy that a shipboard crane is used to deploy it. Digital data links from oceanic buoys to satellites have been used, but the data rates are typically much less than 1 Mbps.
Therefore, a need exists for a low power, high data throughput rate communications system that does not rely on cables between communications nodes that are vulnerable to damage. A further need exists for a data link that may be remotely deployed and which is compact in size and relatively light compared to present systems.
A communications node includes a controller for 1) initializing a counter and resetting a FIFO buffer; 2) determining if a predetermined number of data packets have been transmitted; 3) transmitting the data packets after the FIFO buffer is partially filled if the number of data packets transmitted is less than the predetermined number, incrementing the counter, and returning to step (2); 4) directing a transceiver to be in a receive mode if the predetermined number of data packets have been transmitted; 5) determining if a command signal has been detected; 6) processing a backlink command if a command signal has been detected, and then directing the transceiver to be in transmit mode, clearing the counter, and returning to step (2); and 7) setting the transceiver in a transmit mode if no command signal has been detected, and then clearing the counter and returning to step (2).